...programmers can now get stuck into the source code (direct download, log on required) of two games, "Return to Castle Wolfenstein" and "Wolfenstein: Enemy Territory", which id Software has released under an open source licence. Carmack said The source code of "Doom 3" is to become available after the release of Rage. Earlier this week, id Software completed the beta phase of the free Quake Live online shooter and is now offering paid subscriptions for gaming pros and clans.

Source:
http://www.h-online.com/open/news/item/John-Carmack-ports-Rage-engine-to-iPhone-1058844.html